# Regular Meeting (2022.12.26)

* New 48 fanout board: 2 solutions

## New 48 fanout board

### Sol 1:

* OPA: [AD8397](https://www.analog.com/media/en/technical-documentation/data-sheets/ad8397.pdf)
* 2 OPAs in a package
* BW: 69MHz, Slew Rate: 53V/us
* Controlled ON/OFF by LDO(ADP125)
* 8 channels a group
* Higher current supplies is necessary
* LDO needs \>400mA current output
* \[4.5V/(50ohm + 50ohm)\] \* 8channels = 360mA
* Lower PSRR aka higher noise
* Caused by LDO ADP125
* LDO: [ADP125](https://www.analog.com/media/en/technical-documentation/data-sheets/adp124_125.pdf)
* 500mA max output
* Must add 2 *setup resistor*
* Noise (worse than sol 1)
* 

### Sol 2:

* OPA: [AD8655](https://www.analog.com/media/en/technical-documentation/data-sheets/ad8655_8656.pdf)
* 1 OPAs in a package
* BW: 28MHz, Slew Rate: 11V/us
* LDO: [LP5907](https://www.ti.com/lit/gpn/lp5907)
* 250mA max output
* No *setup resistor* necessart
* Noise (better than sol 1)
* 

### Summery about sol 1 and sol 2

* Higher system bandwidth performance(e.g. slew rate, R/F time) would reduce PSRR aka noise rised. If that's fine, select AD8397(sol 1)
* Higher system PSRR would reduce bandwidth performance. If that's fine, select AD8655(sol 2)
* Because I control OPA output ON/OFF with EN of LDO:
* ON/OFF 4 channels minimum-> Select AD8655(sol 2)
* ON/OFF 8 channels minimum-> Select AD8397(sol 1)

### Common part

* PSU
* EU terminated
* USB 5V with CLC filter
* No filter: 200mVpp ripple
* With filter: 100mVpp ripple
* 4.5V output for LDO
* Switch 8/4 channel of a OPA
* Odd/Even channels
* *DIP Switch* with *EN of LDO*

###### tags: `Regular Meeting` `DeWei`